1. Field of the Invention
The invention relates to a multisectional lifting piston for internal-combustion engines, in particular those in which the translatory movement of two opposing, synchronous pistons is converted into rotation by a slide crank drive, with a piston rod rigidly connected to the two pistons, as is described and illustrated for example in German Pat. specification No. 920,758.
2. Description of the Invention
Many configurations of internal-combustion engine lifting pistons made of several individual parts are known in what is called high-power engine construction. There, multisectional working pistons have been used for some time. The reasons lie in the different loads to which the engine piston is subjected. For instance, the piston head with its fire land is subjected to alternating thermal stresses and static pressures. In addition, the piston as a whole comes under high dynamic acceleration and deceleration forces. In the case of engines with slider-crank mechanisms, in particular in the case of short stroke engines, great bending forces bear on the piston skirt on account of the high normal pressures.
Since ceramic has recently also been accepted as a material in engine construction and with such so-called ceramic engines all parts in sliding contact with one another have to be made of the same material, in other words the necessary piston ring also has to be produced from ceramic, there arises the problem of fitting such piston rings. As experience shows, the elasticity of such piston rings is not sufficient for them to be stripped over the piston skirt to bring them into the piston's annular groove.